/**
 * @file
 * AutoIP Automatic LinkLocal IP Configuration
 *
 */

/*
 *
 * Copyright (c) 2007 Dominik Spies <kontakt@dspies.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * Author: Dominik Spies <kontakt@dspies.de>
 *
 * This is a AutoIP implementation for the lwIP TCP/IP stack. It aims to conform
 * with RFC 3927.
 *
 *
 * Please coordinate changes and requests with Dominik Spies
 * <kontakt@dspies.de>
 */

/*******************************************************************************
 * USAGE:
 * 
 * define LWIP_AUTOIP 1  in your lwipopts.h
 * 
 * If you don't use tcpip.c (so, don't call, you don't call tcpip_init):
 * - First, call autoip_init().
 * - call autoip_tmr() all AUTOIP_TMR_INTERVAL msces,
 *   that should be defined in autoip.h.
 *   I recommend a value of 100. The value must divide 1000 with a remainder almost 0.
 *   Possible values are 1000, 500, 333, 250, 200, 166, 142, 125, 111, 100 ....
 *
 * Without DHCP:
 * - Call autoip_start() after netif_add().
 * 
 * With DHCP:
 * - define LWIP_DHCP_AUTOIP_COOP 1 in your lwipopts.h.
 * - Configure your DHCP Client.
 *
 */

#include "lwip/opt.h"

#if LWIP_AUTOIP			/* don't build if not configured for use in lwipopts.h */

#include "lwip/mem.h"
#include "lwip/udp.h"
#include "lwip/ip_addr.h"
#include "lwip/netif.h"
#include "lwip/autoip.h"
#include "netif/etharp.h"

#include <stdlib.h>
#include <string.h>

/* Pseudo random macro based on netif informations.
 * You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
#ifndef LWIP_AUTOIP_RAND
#define LWIP_AUTOIP_RAND(netif) ( (((u32_t)((netif->hwaddr[5]) & 0xff) << 24) | \
                                   ((u32_t)((netif->hwaddr[3]) & 0xff) << 16) | \
                                   ((u32_t)((netif->hwaddr[2]) & 0xff) << 8) | \
                                   ((u32_t)((netif->hwaddr[4]) & 0xff))) + \
                                   (netif->autoip?netif->autoip->tried_llipaddr:0))
#endif /* LWIP_AUTOIP_RAND */

/* static functions */
static void autoip_handle_arp_conflict (struct netif *netif);

/* creates random LL IP-Address for a network interface */
static void autoip_create_rand_addr (struct netif *netif,
				     struct ip_addr *RandomIPAddr);

/* sends an ARP announce */
static err_t autoip_arp_announce (struct netif *netif);

/* configure interface for use with current LL IP-Address */
static err_t autoip_bind (struct netif *netif);

/**
 * Initialize this module
 */
void
autoip_init (void)
{
  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | 3, ("autoip_init()\n"));
}

/**
 * Handle a IP address conflict after an ARP conflict detection
 */
static void
autoip_handle_arp_conflict (struct netif *netif)
{
  /* Somehow detect if we are defending or retreating */
  unsigned char defend = 1;	/* tbd */

  if (defend)
    {
      if (netif->autoip->lastconflict > 0)
	{
	  /* retreat, there was a conflicting ARP in the last
	   * DEFEND_INTERVAL seconds
	   */
	  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
		       ("autoip_handle_arp_conflict(): we are defending, but in DEFEND_INTERVAL, retreating\n"));

	  /* TODO: close all TCP sessions */
	  autoip_start (netif);
	}
      else
	{
	  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
		       ("autoip_handle_arp_conflict(): we are defend, send ARP Announce\n"));
	  autoip_arp_announce (netif);
	  netif->autoip->lastconflict =
	    DEFEND_INTERVAL * AUTOIP_TICKS_PER_SECOND;
	}
    }
  else
    {
      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
		   ("autoip_handle_arp_conflict(): we do not defend, retreating\n"));
      /* TODO: close all TCP sessions */
      autoip_start (netif);
    }
}

/**
 * Create an IP-Address out of range 169.254.1.0 to 169.254.254.255
 *
 * @param netif network interface on which create the IP-Address
 * @param RandomIPAddr ip address to initialize
 */
static void
autoip_create_rand_addr (struct netif *netif, struct ip_addr *RandomIPAddr)
{
  /* Here we create an IP-Address out of range 169.254.1.0 to 169.254.254.255
   * compliant to RFC 3927 Section 2.1
   * We have 254 * 256 possibilities
   */

  RandomIPAddr->addr = (0xA9FE0100 + ((u32_t) (((u8_t) (netif->hwaddr[4])) |
					       ((u32_t)
						((u8_t) (netif->hwaddr[5])))
					       << 8)) +
			netif->autoip->tried_llipaddr);

  if (RandomIPAddr->addr > 0xA9FEFEFF)
    {
      RandomIPAddr->addr = (0xA9FE0100 + (RandomIPAddr->addr - 0xA9FEFEFF));
    }
  if (RandomIPAddr->addr < 0xA9FE0100)
    {
      RandomIPAddr->addr = (0xA9FEFEFF - (0xA9FE0100 - RandomIPAddr->addr));
    }
  RandomIPAddr->addr = htonl (RandomIPAddr->addr);

  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
	       ("autoip_create_rand_addr(): tried_llipaddr=%" U16_F ", 0x%08"
		X32_F "\n", (u16_t) (netif->autoip->tried_llipaddr),
		(u32_t) (RandomIPAddr->addr)));
}

/**
 * Sends an ARP announce from a network interface
 *
 * @param netif network interface used to send the announce
 */
static err_t
autoip_arp_announce (struct netif *netif)
{
  return etharp_raw (netif, (struct eth_addr *) netif->hwaddr, &ethbroadcast,
		     (struct eth_addr *) netif->hwaddr,
		     &netif->autoip->llipaddr, &ethzero,
		     &netif->autoip->llipaddr, ARP_REQUEST);
}

/**
 * Configure interface for use with current LL IP-Address
 *
 * @param netif network interface to configure with current LL IP-Address
 */
static err_t
autoip_bind (struct netif *netif)
{
  struct autoip *autoip = netif->autoip;
  struct ip_addr sn_mask, gw_addr;

  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
	       ("autoip_bind(netif=%p) %c%c%" U16_F " 0x%08" X32_F "\n",
		(void *) netif, netif->name[0], netif->name[1],
		(u16_t) netif->num, autoip->llipaddr.addr));

  IP4_ADDR (&sn_mask, 255, 255, 0, 0);
  IP4_ADDR (&gw_addr, 0, 0, 0, 0);

  netif_set_ipaddr (netif, &autoip->llipaddr);
  netif_set_netmask (netif, &sn_mask);
  netif_set_gw (netif, &gw_addr);

  /* bring the interface up */
  netif_set_up (netif);

  return ERR_OK;
}

/**
 * Start AutoIP client
 *
 * @param netif network interface on which start the AutoIP client
 */
err_t
autoip_start (struct netif * netif)
{
  struct autoip *autoip = netif->autoip;
  err_t result = ERR_OK;

  if (netif_is_up (netif))
    {
      netif_set_down (netif);
    }

  /* Set IP-Address, Netmask and Gateway to 0 to make sure that
   * ARP Packets are formed correctly
   */
  netif->ip_addr.addr = 0;
  netif->netmask.addr = 0;
  netif->gw.addr = 0;

  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
	       ("autoip_start(netif=%p) %c%c%" U16_F "\n", (void *) netif,
		netif->name[0], netif->name[1], (u16_t) netif->num));
  if (autoip == NULL)
    {
      /* no AutoIP client attached yet? */
      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE,
		   ("autoip_start(): starting new AUTOIP client\n"));
      autoip = mem_malloc (sizeof (struct autoip));
      if (autoip == NULL)
	{
	  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE,
		       ("autoip_start(): could not allocate autoip\n"));
	  return ERR_MEM;
	}
      memset (autoip, 0, sizeof (struct autoip));
      /* store this AutoIP client in the netif */
      netif->autoip = autoip;
      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE,
		   ("autoip_start(): allocated autoip"));
    }
  else
    {
      autoip->state = AUTOIP_STATE_OFF;
      autoip->ttw = 0;
      autoip->sent_num = 0;
      memset (&autoip->llipaddr, 0, sizeof (struct ip_addr));
      autoip->lastconflict = 0;
    }

  autoip_create_rand_addr (netif, &(autoip->llipaddr));
  autoip->tried_llipaddr++;
  autoip->state = AUTOIP_STATE_PROBING;
  autoip->sent_num = 0;

  /* time to wait to first probe, this is randomly
   * choosen out of 0 to PROBE_WAIT seconds.
   * compliant to RFC 3927 Section 2.2.1
   */
  autoip->ttw =
    (u16_t) (LWIP_AUTOIP_RAND (netif) %
	     (PROBE_WAIT * AUTOIP_TICKS_PER_SECOND));

  /*
   * if we tried more then MAX_CONFLICTS we must limit our rate for
   * accquiring and probing address
   * compliant to RFC 3927 Section 2.2.1
   */

  if (autoip->tried_llipaddr > MAX_CONFLICTS)
    {
      autoip->ttw = RATE_LIMIT_INTERVAL * AUTOIP_TICKS_PER_SECOND;
    }

  return result;
}

/**
 * Stop AutoIP client
 *
 * @param netif network interface on which stop the AutoIP client
 */
err_t
autoip_stop (struct netif * netif)
{
  netif->autoip->state = AUTOIP_STATE_OFF;
  netif_set_down (netif);
  return ERR_OK;
}

/**
 * Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds
 */
void
autoip_tmr ()
{
  struct netif *netif = netif_list;
  /* loop through netif's */
  while (netif != NULL)
    {
      /* only act on AutoIP configured interfaces */
      if (netif->autoip != NULL)
	{
	  if (netif->autoip->lastconflict > 0)
	    {
	      netif->autoip->lastconflict--;
	    }

	  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE,
		       ("autoip_tmr() AutoIP-State: %" U16_F ", ttw=%" U16_F
			"\n", (u16_t) (netif->autoip->state),
			netif->autoip->ttw));

	  switch (netif->autoip->state)
	    {
	    case AUTOIP_STATE_PROBING:
	      if (netif->autoip->ttw > 0)
		{
		  netif->autoip->ttw--;
		}
	      else
		{
		  if (netif->autoip->sent_num == PROBE_NUM)
		    {
		      netif->autoip->state = AUTOIP_STATE_ANNOUNCING;
		      netif->autoip->sent_num = 0;
		      netif->autoip->ttw =
			ANNOUNCE_WAIT * AUTOIP_TICKS_PER_SECOND;
		    }
		  else
		    {
		      etharp_request (netif, &(netif->autoip->llipaddr));
		      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
				   ("autoip_tmr() PROBING Sent Probe\n"));
		      netif->autoip->sent_num++;
		      /* calculate time to wait to next probe */
		      netif->autoip->ttw =
			(u16_t) ((LWIP_AUTOIP_RAND (netif) %
				  ((PROBE_MAX -
				    PROBE_MIN) * AUTOIP_TICKS_PER_SECOND)) +
				 PROBE_MIN * AUTOIP_TICKS_PER_SECOND);
		    }
		}
	      break;

	    case AUTOIP_STATE_ANNOUNCING:
	      if (netif->autoip->ttw > 0)
		{
		  netif->autoip->ttw--;
		}
	      else
		{
		  if (netif->autoip->sent_num == 0)
		    {
		      /* We are here the first time, so we waited ANNOUNCE_WAIT seconds
		       * Now we can bind to an IP address and use it
		       */
		      autoip_bind (netif);
		    }

		  if (netif->autoip->sent_num == ANNOUNCE_NUM)
		    {
		      netif->autoip->state = AUTOIP_STATE_BOUND;
		      netif->autoip->sent_num = 0;
		      netif->autoip->ttw = 0;
		    }
		  else
		    {
		      autoip_arp_announce (netif);
		      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
				   ("autoip_tmr() ANNOUNCING Sent Announce\n"));
		      netif->autoip->sent_num++;
		      netif->autoip->ttw =
			ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
		    }
		}
	      break;
	    }
	}
      /* proceed to next network interface */
      netif = netif->next;
    }
}

/**
 * Handles every incoming ARP Packet, called by etharp_arp_input.
 *
 * @param netif network interface to use for autoip processing
 * @param hdr Incoming ARP packet
 */
void
autoip_arp_reply (struct netif *netif, struct etharp_hdr *hdr)
{
  LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | 3, ("autoip_arp_reply()\n"));
  if ((netif->autoip != NULL) && (netif->autoip->state != AUTOIP_STATE_OFF))
    {
      /* when ip.src == llipaddr && hw.src != netif->hwaddr
       *
       * when probing  ip.dst == llipaddr && hw.src != netif->hwaddr
       * we have a conflict and must solve it
       */
      struct ip_addr sipaddr, dipaddr;
      struct eth_addr netifaddr;
      netifaddr.addr[0] = netif->hwaddr[0];
      netifaddr.addr[1] = netif->hwaddr[1];
      netifaddr.addr[2] = netif->hwaddr[2];
      netifaddr.addr[3] = netif->hwaddr[3];
      netifaddr.addr[4] = netif->hwaddr[4];
      netifaddr.addr[5] = netif->hwaddr[5];

      /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
       * structure packing (not using structure copy which breaks strict-aliasing rules).
       */
      MEMCPY (&sipaddr, &hdr->sipaddr, sizeof (sipaddr));
      MEMCPY (&dipaddr, &hdr->dipaddr, sizeof (dipaddr));

      if ((netif->autoip->state == AUTOIP_STATE_PROBING) ||
	  ((netif->autoip->state == AUTOIP_STATE_ANNOUNCING) &&
	   (netif->autoip->sent_num == 0)))
	{
	  /* RFC 3927 Section 2.2.1:
	   * from beginning to after ANNOUNCE_WAIT
	   * seconds we have a conflict if
	   * ip.src == llipaddr OR
	   * ip.dst == llipaddr && hw.src != own hwaddr
	   */
	  if ((ip_addr_cmp (&sipaddr, &netif->autoip->llipaddr)) ||
	      (ip_addr_cmp (&dipaddr, &netif->autoip->llipaddr) &&
	       !eth_addr_cmp (&netifaddr, &hdr->shwaddr)))
	    {
	      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
			   ("autoip_arp_reply(): Probe Conflict detected\n"));
	      autoip_start (netif);
	    }
	}
      else
	{
	  /* RFC 3927 Section 2.5:
	   * in any state we have a conflict if
	   * ip.src == llipaddr && hw.src != own hwaddr
	   */
	  if (ip_addr_cmp (&sipaddr, &netif->autoip->llipaddr) &&
	      !eth_addr_cmp (&netifaddr, &hdr->shwaddr))
	    {
	      LWIP_DEBUGF (AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
			   ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
	      autoip_handle_arp_conflict (netif);
	    }
	}
    }
}

#endif /* LWIP_AUTOIP */
